Signalling information transportation is very important to a communication system. If some of the signaling information is lost, it will have great impact on payload data demodulation. If the channel environment is noisy, the proper protection of signalling information is necessary. For example, DVB-T (Digital Video Broadcast-Terrestrial), DTMB (Digital Terrestrial Multimedia Broadcast, Chinese Terrestrial standard) and the latest DVB-T-2 standard all define signaling protection.
Digital Video Broadcasting-Cable (DVB-C) is a first generation cable transmission system (e.g., see EN 300 429 V. 1.2.1 (1998 April) Digital Video Broadcasting (DVB); Framing structure, channel coding and modulation for cable systems). However, migration to a second generation cable system, DVB-C2, is currently being studied for protecting the signalling information.
FIG. 1 is a schematic diagram showing a L1 (layer1) signaling structure used in a DVB-T2 OFDM frame. As shown in FIG. 1, the signaling information is split into three main sections: P1 signalling, L1 pre-signalling and L1 post-signalling. The P1 signalling is carried by P1 symbols, and used to indicate the transmission type and basic transmission parameters. The remaining signalling is carried out by P2 symbols, comprising L1 pre-signalling and L1 post-signalling. The L1 pre-signalling enables the reception and decoding of the L1 post-signalling, which in turn conveys parameters needed by the receiver to the access physical layer pipes. The L1 post-signalling is further split into two main parts: configurable and dynamic, and these may be followed by an optional extension field. The L1 post-signalling finishes with a CRC and padding (if necessary).
In order to protect the L1 signalling information of the OFDM frame in DVB-T2, a concatenation channel code was proposed for performing FEC (Forward Error Correction) encoding for the signaling information, with the inner code using punctured S2-LDPC codes and the outer code using shortened BCH codes. This protection scheme can reuse the codex used for the following data payload of the OFDM frame. From the above-mentioned description, it can be seen that signaling information is protected at the OFDM frame level in DVB-T2. In addition, for DTMB and DVB-T, signaling information is also protected at the OFDM frame level.